Description

Yanmar 3YM20 4‑Stroke Marine Diesel Engine (Inboard)

The Yanmar 3YM20 is a compact yet powerful 3‑cylinder, 4‑stroke marine diesel engine designed for inboard applications on small to medium boats. With a rated output of 15.3 kW (approx. 21 HP) at 3600 rpm, it delivers smooth, efficient power while meeting global emissions standards for recreational vessels.

Built with a naturally aspirated, vertical water‑cooled design, the 3YM20 offers quiet, vibration‑reduced operation and dependable performance, supported by a freshwater cooling system with heat exchanger and an indirect injection combustion system for reliable fuel delivery. Maintenance is simplified with service components—like the water pump, fuel filter, oil change access, and dipstick—grouped on the same side of the engine.

Standard features include a 12 V electric starter and 125 A alternator, flexible mounts, expansion tank, and basic control panel, while optional accessories—such as high‑riser mixing elbows, extended wire harnesses, dual station controls, and hot water kits—allow customization for specific installations. The engine can also be paired with Yanmar’s double–seal saildrive system (model 3YM20C) for sailboats, offering a choice of forward and reverse gear ratios to match vessel needs.

Designed for fuel efficiency, durability, and ease of installation, the Yanmar 3YM20 remains a versatile diesel powerplant for pleasure craft, fishing boats, and sailboat auxiliary propulsion.

Specifications:

Combustion System: Indirect Injection
Cylinders: In-line
Direction Of Rotation [Crankshaft]: Counterclockwise Viewed From Stern
Lubrication System: Enclosed, Forced Lubricating System
Starting System: Electric Starting 12V – 1.4 kW
Configuration: 4-Stroke, Vertical, Water-Cooled Diesel Engine
Maximum Output At Crankshaft: * 15.3 kW@3600 rpm [21 mhp@3600 rpm]
Displacement: 0.854 L [52.1 cu in]
Bore X Stroke: 70 mm x 74 mm, [2.76 in x 2.91 in]
Aspiration: Natural Aspiration
Cooling System: Fresh Water Cooling With Heat Exchanger
Dry Weight Without Gear: 110 kg [243 lbs]
Engine Mounting: Rubber Type Flexible Mounting
Factory Warranty: 5 Years Extended Warranty

Package Include:

Set of flexible mounts
Exhaust mixing elbow [L-type]
Belt safety cover
Expansion tank for fresh water cooling system
Alternator 12V – 125A
Electric stop solenoid
Operation manual
Sensor for instrument panel
B20-panel
Choice Of Transmissions: KM2P-1 (parallel) or Saildrive [SD25]